Piezoelectricity is referred as the electric charge that accumulates in certain solid materials (such as crystals, certain ceramics etc.) in response to applied mechanical stress. In general, ‘piezoelectricity’ means electricity resulting from application of pressure and vice-versa and has useful applications such as in the production and detection of sound, generation of high voltages, electronic frequency generation, microbalances, to drive an ultrasonic nozzle, and ultrafine focusing of optical assemblies.
Piezoelectric compositions have been widely investigated and used in a variety of piezoelectric components like transducers, ultrasonic receivers, generators etc. Consequently, the use of piezoelectric ceramic compositions to form piezocomponents is increasing. Piezoelectric compositions having higher electromechanical coupling efficiency (kp>0.56), mechanical quality factor (Qm>500) and low dielectric loss (tan δ≤0.004) are in great demand for high power applications. Piezoelectric components for transducers demand piezoelectric compositions that can also yield enhanced insulation resistance, IR≥10 GΩ. Existing high power piezoelectric ceramics do not simultaneously exhibit suitable electromechanical properties and high insulation resistance. In the current state of art, the existing piezoelectric components that exhibit sufficiently high electromechanical characteristics have low insulation resistance, usually ≤10 GΩ, which is not adequate especially for high power transducer applications.
The piezoelectric properties of piezoelectric elements can be varied by addition of certain foreign constituents. Sintering cycles and poling process have an effect on fabrication of piezoelement of desired physical properties and electromechanical characteristics. However, it is difficult to optimise these processes to fabricate specific piezoceramic components having desired electromechanical characteristics as well as high IR. In other words, it is technically very difficult to prepare a piezoelectric component through a known set of process parameters. Therefore, the development of new piezoceramic composition and its intended application often demand practising of a different fabrication method because processing methods can have influence on the physical and electromechanical characteristics of piezoceramics.
As piezoelements are sought after in various applications, the demand for new piezoelectric compositions and piezoelectric components derived from them is very important. However, the need of the hour is that the piezoelectric compositions and the corresponding piezocomponents must possess improved insulation resistance along with high electromechanical characteristics.
U.S. Pat. No. 3,376,226 claims piezoelectric ceramic composition having a solid solution of lead-zirconate titanate-stannate modified by adding thorium oxide and chromium oxide improving electro mechanical coupling factor(kp˜0.59) and providing mechanical quality factor (Qm˜400).
U.S. Pat. No. 3,268,453 relates to piezoelectric ceramic compositions of ternary and binary systems containing solid solutions of PMN-PT-PZ modified by additional constituents and articles of manufacture fabricated therefrom. In addition, several patents such as U.S. Pat. Nos. 3,546,120, 3,649,540, 3,890,241 relate to piezoceramic compositions having piezoelectric properties meeting the specific application fields of transducers, sensors etc.
It is clear from the above discussion that piezoceramic compositions are known in the art for various applications. However, the simultaneous requirements of high insulation resistance and improved electromechanical characteristicsare not met by the piezocomponents of the prior art. Accordingly, there has been a continuing need in the art to provide better and significantly improved piezoceramic systems having high values of electromechanical coupling efficiency and mechanical quality factor along with very large insulation resistance in component form. The present disclosure aims at overcoming the aforesaid drawbacks of the prior art.